The instrument requested is a BD LSR-Fortessa, a high dimensional flow cytometer with 5 lasers, for the acquisition of 20 different parameters, and ability to perform detailed phenotypical and functional characterization of cellular populations and subsets. Given the myriad of cell types that have been identified in the peripheral blood and other tissue compartments, the ability of standard flow cytometers in characterizing these cells in a comprehensive manner would require a collection of large amount of blood or other biological specimens. Use of a high dimensional cytometer not only decreases dramatically this requirement, but also facilitates the discovery of new cellular populations, that otherwise would not be identified by low dimensional immunophenotyping. This is possible thanks to simultaneous assessment of cell surface proteins, intracellular phosphoproteins, cytokines, nuclear factors and other functional readouts. The ability of high dimensional cytometers to finely define cellular subsets (e.g. T cells, B cells) from complex mixtures such as blood and tissues, improves the likelihood of identifying cells relevant in disease pathogenesis, vaccination, and response to clinical treatment. This particular attribute is necessary to tackle and dissect complex conditions that arise during ageing (e.g. neurodegeneration) and diseases such HIV and cancer and that are currently investigated by VA researchers at the STVHCS. This instrument will be used to support the following research projects of the following VA researchers: (1) Sunil K. Ahuja M.D. - Host Genetic Determinants of HIV Pathogenesis (NIH/NIAID MERIT Award), Immune responses and host defenses in a large US HIV- population of military relevance [U.S. Air Force Medical Service Research Program (59th Medical Wing Intramural Award] and Center for Personalized Medicine: Systems of Biology of Inflammation and Immunity (VA ORD). (2) Robert Clark M.D. -Analysis of Olfactory Dysfunction for Early Diagnosis of Parkinson's Disease (VA Merit). (3) Senlin Li, M.D. - Macrophage-mediated gene delivery of neurotrophic factors for Parkinson's disease (VA Merit). (4) James Freeman, Ph.D. - Role of CD44 in adaptive plasticity of pancreatic cancer (VA Merit). (5) Ricardo Aguiar, M.D., Ph.D. - Non-coding RNAs at the interface of aberrant NF-kB signals and lymphomagenesis (VA Merit). This instrument will also be used as a focal point to form collaborations among and between these investigators, as well as recruitment of new investigators into the STVHCS.